(1) Field of the Invention
The present invention relates to a system and a method for rapidly preheating an automotive fuel cell and more particularly, to a system and method which utilizes heat generated by a vehicle air compressor to selectively and rapidly heat a vehicle's fuel cell stack.
(2) Background of the Invention
In order to reduce undesirable emissions and the demand for fossil fuel, automotive vehicles have been designed that are powered by electrical devices such as fuel cells. These “fuel cell-powered electric vehicles” reduce emissions and the demand for conventional fossil fuels by eliminating the internal combustion engine (e.g., in completely electric vehicles) or by operating the engine at only its most efficient/preferred operating points (e.g., within hybrid electric vehicles).
Many fuel cells consume hydrogen gas and air (e.g., as reaction constituents). The consumed hydrogen and air must be properly stored and transferred to the fuel cell at certain temperatures and pressures in order to allow the fuel cell and vehicle to operate in an efficient manner.
Vehicles employing these types of fuel cells often include systems and/or assemblies for storing and transmitting hydrogen gas and air to the fuel cell. Particularly, the hydrogen gas is typically stored within a tank at a relatively high pressure and with a relatively high amount of potential energy. The hydrogen gas is then transferred to the fuel cell by use of several conduits and several pressure-reducing regulators, which lower the pressure of the gas by a desirable amount. The air that is communicated from the fuel cell is obtained at atmospheric pressures and must be pressurized or otherwise driven through the system in order to ensure proper and efficient fuel cell operation. This pressurization and/or driving of air through the system is typically performed by use of a compressor or turbine. These compressors or turbines compress the air to a desired or predetermined pressure, which causes the air to increase in temperature. Because air above a certain temperature can damage a fuel cell or cause the fuel cell to operate inefficiently, the air is passed through a heat exchanger prior to entering the fuel cell, thereby cooling the air and ensuring the air entering the fuel cell does not exceed a predetermined temperature (e.g., 80 degrees Celsius).
In certain conditions, such as cold starting or freezing conditions, it is desirable to heat a vehicle's fuel cells in order to ensure that the fuel cells operate efficiently in a minimal amount of time. Various schemes exist to overcome the cold starting limitations of fuel cells and/or to maintain fuel cells at or above a certain desired temperature. Certain prior vehicles utilize an auxiliary power source, such as resistive heating elements powered by on-board batteries. However, these additional power sources adversely increase the cost, weight and volume of the fuel cell system, drain the vehicle's battery, and consume electrical energy, which could otherwise be used to power the vehicle's electrical components and accessories. Other prior schemes for pre-heating fuel cells include introducing a hydrogen/air mixture into the process oxidant channels of the fuel cell. However, these prior schemes require complex control systems which undesirably increase the cost and complexity of the vehicle.
There is therefore a need for a new and improved system and method for use with a fuel cell powered vehicle which selectively and rapidly preheats the vehicle's fuel cell stack during cold starting or freezing conditions.